1. Field of the Invention
The invention relates to new antitartar agents, dentifrice compositions containing these agents and use of such compositions to control tartar accumulation on teeth.
2. The Related Art
Tartar, known also as calculus, is a hard, mineralized deposit which forms around teeth. This formation arises from deposition of crystals of calcium phosphate in the pellicle and extracellular matrix of dental plaque. Various forms of calcium phosphate have been identified but the most difficult to remove and thermodynamically most stable form is called hydroxyapatite (HAP). Amorphous forms of calcium phosphate are believed to be the precursors of HAP. Regular brushing can usually remove the amorphous forms but is not fully effective to dislodge the final stable calculus form. Therefore it is desirable to prevent amorphous forms of calcium phosphate from transforming into HAP. The art has recognized that agents which interfere with the formation of HAP crystallization will be effective antitartar agents.
Polymers, especially those of the anionic type, have been found to be effective antitartar agents. U.S. Pat No. 4,661,341 (Benedict et al) discloses polyacrylic acids of molecular weight 3500 to 7500 for use in oral antitartar compositions. Comonomers specified include hydroxyalkyl acrylates or methacrylates and acrylamides. U.S. Pat. No. 3,429,963 (Shedlovsky) teaches use of maleate-containing copolymers and vinyl sulfonates in oral compositions. Typically, low molecular weight anionic materials of high charge density are preferred in the known art. For example, U.S. Pat. No. 4,183,914 (Gaffar et al) discloses use of polymaleates as antitartar agents; however, these materials cannot be obtained above molecular weight 1000, and often have low purity in commercial samples. These polymeric materials have poor appearance, taste, and safety as a consequence of high impurity levels deriving from the manufacturing process.
Polymers have also been found to give benefits other than crystal-growth or transformation inhibition. Gaffar et al. in a series of patents reports use of synthetic linear anionic polymers of higher molecular weight for use in combination with inorganic pyrophosphates in oral compositions. See U.S. Pat. No. 4,627,977; U.S. Pat. No. 4,806,340; U.S. Pat. No. 4,806,342; U.S. Pat. No. 4,808,400 and U.S. Pat. No. 4,808,401. These polymers were found to inhibit the action of pyrophosphatase in the mouth thereby allowing greater efficacy of the pyrophosphate. Preferred were the methyl vinyl ether/maleic anhydride copolymers sold by GAF Corporation under the Gantrez trademark. These materials have molecular weights which are between 50-500,000, although a broader range (1000 to 1 million) is specified in the patents.
Other polymers have been found to inhibit the growth or adhesion of microbials, resulting in reductions of plaque and therefore degree of tartar buildup. Sipos et al. in U.S. Pat. No. 4,364,927 and U.S. Pat. No. 4,361,547 discloses several types of sulfonated aromatic polymers which are effective in reducing plaque formation.
Thus, most of the prior art teaches polymeric materials which are either good crystal growth inhibitors or good antiplaque agents. It would be beneficial to have polymeric agents which were effective in both functions, i.e., effectively inhibit transformation of brushite to hydroxyapatite, and in addition reduce plaque buildup on oral surfaces.
Accordingly it is an object of the present invention to provide an antitartar agent functioning both to inhibit transformation of brushite to hydroxyapatite and also to reduce plaque buildup on oral surfaces.
A further object of the present invention is to provide new oral compositions and a method for more effectively controlling buildup of plaque and tartar on teeth.
These and other objects of the present invention will become more readily apparent in view of the detailed description and Examples which follow.